The present invention relates to a blank for an axle beam, a wheel suspension, and a method for manufacturing an axle beam. It especially relates to a blank for an axle beam which is configured so as to be usable for both steerable wheel axles and fixed, non-steerable wheel axles, and to wheel suspensions comprising a machined such blank, and to a method for providing an axle beam from such a blank.
Axle beams are used to support wheel axles in vehicles. In the manufacture of heavy-duty vehicles such as, for example, trucks, high demands are placed upon flexibility for the satisfaction of specific customer requirements, so that the vehicle is adaptable to different applications. For this purpose, vehicles, especially trucks, are manufactured with both steerable wheel axles and non-steerable, fixed wheel axles. An example of such axles which can be configured so as to be both steerable and non-steerable is a non-driven pusher axle in a commercial vehicle.
According to the prior art, specific blanks are provided for axle beams for steered and non-steered wheel axles respectively. This means that two sets of blanks for axle beams must be stocked, which adds to the handling costs. In addition, it is more complicated to change a decision on the extent to which the axle beam shall be configured with fixed or steered wheel axle. In order to reduce the problems associated with separate stock-keeping, it has therefore been proposed to use the same axle beam for both steered and non-steered beams and to instead fix a wheel spindle, which is fitted to the axle beam, using a rod which connects the wheel spindle to the beam structure of the truck. The rod is therefore fastened at both its ends with a respective joint. The hitherto known solution has drawbacks in that a plurality of joints need to be provided and in that it is difficult to configure rod and fastening with sufficient precision, which means that the wheel can come to be set somewhat obliquely, possibly leading to increased fuel consumption. The known solutions have exhibited drawbacks as a result of the construction having become heavy, expensive and bulky, nor was it well matched to its unique application. Since the position of the wheels could not easily be set with sufficient precision, known solutions have sometimes caused unnecessary tire wear as a result of incorrect mounting of the wheels.
It is desirable to provide blanks for axle beams which can be used for both fixed, non-steerable wheel axles and for steerable wheel axles and by which the above problems are solved.
According to an aspect of the invention, a continuous blank, made in one piece, is used, which at each end has a bushing, comprising a bearing for a kingpin, and lug-shaped protrusions situated on each side of a plane through the longitudinal axes of said bushings. The lug-shaped protrusions have a first part, which, following machining of the lug-shaped protrusion, is suitable for use as a locking surface for a wheel-spindle, should the axle beam be used to support a fixed, non-steerable wheel axle, and that said lug-shaped protrusions have a second part, which is suitable for use as an end stop for limiting the deflection of the rotary motion of a wheel spindle after the lug-shaped protrusion is at least partially machined away, should the axle beam be used to support a steerable wheel axle. The same blank is therefore used for both steered and non-steered wheel axles. By machining is meant that material removes from the integrally made blank. Machining can be realized, for example, by milling, boring and grinding. Both the end stops for deflection limitation alternatively locking surfaces for the wheel spindle can thereby be formed from the lug-shaped protrusion. The fact that the locking surface is situated directly on the beam and is formed integrally therewith means that the wheel can be locked with good stability. In addition, machining can be realized with good precision, whereby the risk of tilting is reduced compared to if locking is realized via a rod.
In general terms, this can be explained by the fact that it is easier to achieve good accuracy if fewer components interact, since, with fewer components, the overall error tolerance is reduced. In addition, the placement of the surfaces which constitute end stops can be easily adapted to different requirements in respect of different vehicles, since the machining of the lug-shaped protrusion can then easily be adapted such that a different amount of material is machined away, in which case the end stop will be placed in the desired location. For the purpose of providing a locking surface, alternatively an end stop, the lug-shaped protrusion has a first part, which, following machining of the lug-shaped protrusion, is suitable for use as a locking surface, and a second part, which is suitable for use as an end stop for limiting the deflection of a rotary motion of a wheel spindle.
An axle beam for a steered wheel axle, alternatively a fixed, non-steered wheel axle, can therefore be formed from one blank.
The first part of the lug-shaped protrusion preferably lies farther from a midpoint of the axle beam in the longitudinal direction of the axle beam than does the second part. As a result of this configuration, the first part will lie closer to that surface of a wheel spindle which directly faces the axle beam than does the second part. In the event of an imaginary rotary motion of the wheel spindle about the kingpin in the clockwise or counterclockwise direction, the wheel spindle will come into contact with the first part before it comes into contact with the second part. Because of this, the first part can be configured to lock the wheel spindle of a non-steerable wheel axle and the second part can be configured to limit the rotary motion at an intended stop position for a steerable wheel axle. In order to use the blank for a steered wheel axle, the lug-shaped protrusion must therefore be machined such that the first part is removed. In this way, the wheel spindle is not secured against rotation, but rather a certain predetermined rotation is allowed up to the point where the end stop prevents further rotation. When the blank is to be used for an axle beam for a fixed axle, the second part does not-need to be removed. In this case, the second part must still be machined such that a bolt can be inserted through the first part, through a washer lying between the first part, and can be fastened in the wheel spindle for the application of a clamping force between the first part and the wheel spindle and thereby secure the wheel spindle against rotation. In this case, the second part is at least partially machined away in order to liberate a bearing surface for a fixing bolt in the first part, should the axle beam be used to support a fixed, non-steerable wheel axle.
In order easily to achieve locking between wheel spindle and axle beam, a locking surface of the first part is preferably placed beyond the center point, in the longitudinal direction of the axle beam, of a longitudinal axis of the bushing constituting a bearing for the kingpin.
Preferably, the lug-shaped protrusion is configured as shown in FIG. 2, i.e., with a nose-like shape having a narrower, lower, inner second part and a wider, taller, outer first part. By the first part being wider is meant that the first part has a greater extent along a longitudinal axis of the bushing constituting a bearing for the kingpin than does the second part. By the first part being taller is meant that the extent perpendicular to the longitudinal direction of the axle beam and perpendicular to said longitudinal axis of bushing is greater for the first part than the second part. The lug-shaped protrusion is in this case configured in a continuous piece comprising said first and second part and an intermediate piece in which the first part merges into the second part.
In the manufacture of an axle beam for a steerable wheel axle and an axle beam from a fixed, non-steerable wheel axle respectively, the protrusion is machined. In the first case, machining is carried out to provide a deflection-limiting surface and, in the second case, to provide a plane locking surface.
The invention also relates to a wheel suspension comprising a machined blank according to the above, which blank has been machined for use as an axle beam for a steerable wheel axle, and to a wheel suspension comprising a machined blank according to the above, which blank has been machined for use as an axle beam for a fixed, non-steerable wheel axle.
The invention also relates to a method for providing an axle beam for a steered wheel axle, alternatively an axle beam for a fixed, non-steered wheel axle, from the same blank.